ApiDiscovery: Fix response add response class that will hold api response

Signed-off-by: Rohit Yadav <bhaisaab@apache.org>
ApiDiscovery: Fix listApis to return api response, related apis etc.

- Fix method to return listApis per api name basis
- Return api response, api related cmd etc. as part of response
- Caching and processing all cmd, response classes when plugin starts, made class
  list, maps static so they are shared by multiple instances in case, takes about
  1306ms to do the processsing but only on load time
- Cache for first listApi() and return precached data thereon, takes 2.2ms
  for first call, during runtime and 0ms thereon

Signed-off-by: Rohit Yadav <bhaisaab@apache.org>